1. Field of the Invention
The present invention relates to a soft magnetic film which is used, for example, as a core material of a thin film magnetic head and which is composed of an FeNiMo alloy having a high resistivity and a high saturated magnetic flux density, and to a thin film magnetic head using the soft magnetic film described above.
2. Description of the Related Art
In planar magnetic elements such as a thin film magnetic head or a thin film inductor, a NiFe alloy (permalloy) has been used as a magnetic material in many cases.
Since, for example, the NiFe alloy mentioned above has relatively superior soft magnetic properties and is easily formed by plating, the NiFe alloy has become one of soft magnetic materials which are frequently used.
However, concomitant with the recent trend toward a high frequency current of a planar magnetic element, an eddy current loss in a high frequency current region becomes a problem.
In order to reduce the eddy current loss, a soft magnetic film having a high resistivity is advantageously used.
For example, in Japanese Unexamined Patent Application Publication No. 8-212512 (Patent publication 1), in order to reduce an eddy current loss in high frequency recording, a thin film magnetic head composed of a soft magnetic film is disclosed, in which the soft magnetic film has a resistivity of 40 ∥Ω·cm or more by adding molybdenum (Mo) to a binary NiFe alloy.
Patent Publication 1
Japanese Unexamined Patent Application Publication No. 8-212512 (pp. 11 to 12, and FIGS. 16 to 18)
Patent Publication 2
Japanese Unexamined Patent Application Publication No. 9-63016 (pp. 5 to 6, and FIG. 5)
Patent Publication 3
Japanese Unexamined Patent Application Publication No. 2000-235911 (pp. 3 to 4, and FIG. 1)
Patent Publication 4
Japanese Unexamined Patent Application Publication No. 2000-58364
However, in the FeNiMo alloy film disclosed in Japanese Unexamined Patent Application Publication No. 8-212512, when the composition ratio of Fe to Ni is more than 60%, a saturated magnetic flux density Bs is rapidly decreased. As a result, the saturated magnetic flux density Bs of the FeNiMo alloy film disclosed in Japanese Unexamined Patent Application Publication No. 8-212512 is decreased to 1.6 tesla (T) or less. From a theoretical point of view, when the Fe content of an FeNiMo alloy film is increased, the saturated magnetic flux density thereof is also increased; however, it is believed that, according to Japanese Unexamined Patent Application Publication No. 8-212512, a stable FeNiMo alloy film having a composition ratio of Fe to Ni of more than 60% cannot be formed. According to the patent described above, this FeNiMo alloy is formed by direct current plating.
In addition, in Patent Publications 2 to 4, although FeNiMo alloy films are also disclosed, all of them are not stable FeNiMo alloy films having a composition ratio of Fe to Ni of more than 60%.
However, concomitant with the recent trend toward higher recording density, in order to improve recording density, it has been desired that the Fe content in the FeNiMo alloy is further increased so as to further increase the saturated magnetic flux density Bs.